When you enter into full screen mode in Foxit PDF Editor/Foxit PDF Reader by pressing F11, Foxit PDF Editor/Foxit PDF Reader would display the PDF page according to the following rules:
1)If the One page at a time option is checked under Full Screen tab in Preferences dialog box,Foxit PDF Editor/Foxit PDF Reader would always display PDF page with "Single page" and "Fit page" as its default page layout and zoom level.
2)If the One page at a time option is unchecked under Full Screen tab in Preferences dialog box,full screen mode would inherit the page layout and zoom level of the current PDF file in non-full-screen mode directly.In other words,the page layout and zoom level won't be changed after entering into full screen mode.
How to set default viewing layout
Why can't Foxit PhantomPDF/Reader remember the Page Layout Settings in Preferences??
Some factors that affect the page layout display and zoom level in Foxit PDF Reader/Editor